Use single quotation marks for the inner quote if the outer quote uses double quotation marks.
Use double quotation marks for the inner quote if the outer quote uses single quotation marks.
If needed, alternate quotation styles consistently to show each level clearly.
For a quote inside a quote inside a quote, switch styles again or rephrase for clarity.
Keep punctuation placement consistent with the quotation style you are using.
If your style guide requires it, use italics or block quotes instead of nested quotation marks.